Curvature Attribute from Surface-Restoration as Predictor Variable in Kupferschiefer Copper Potentials     

Pablo Mejía-Herrera  Jean-Jacques Royer  Guillaume Caumon  Alain Cheilletz 《Natural Resources Research》2015,24(3):275-290

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Late Pleistocene (MIS 3–4) climate inferred from micromammal communities and δO of rodents from Les Pradelles,France     

Aurélien Royer  Christophe Lécuyer  Sophie Montuire  Gilles Escarguel  François Fourel  Alan Mann  Bruno Maureille 《Quaternary Research》2013

The middle Paleolithic stratigraphic sequence of Les Pradelles (Charente, France) spans from the end of Marine Isotope Stage (MIS) 4 until the middle of MIS 3. Micromammal remains are present in all the stratigraphic levels, offering a rare opportunity to address the questions of both environmental and climatic fluctuations throughout this period. Climate modes were studied through the taphonomy, biodiversity and oxygen isotope compositions of phosphate (δ¹⁸O_p) from 66 samples of rodent tooth enamel. The δ¹⁸O_p values from the lower sedimentary levels provide summer mean air temperatures of 19 ± 2°C (level 2/1) and of 16 ± 2°C (levels 2A, 2B and 4A). Within the middle of sequence (level 4B), a paleobiodiversity change can be identified with an increase of Dicrostonyx torquatus, which is associated with the largest amplitude in δ¹⁸O_p values and the highest maximal δ¹⁸O_p values. At the top of the sequence (level 5-2), a biodiversity change is observed with the increase of Microtus arvalis, but without any change in δ¹⁸O_p values. The association of cold rodent species with unexpected high and large amplitudes in the δ¹⁸O_p values of their teeth, possibly indicative of aridity, suggests their deposition during a Heinrich event.  相似文献   

Seasonal variability of cohesive sediment aggregation in the Bach Dang–Cam Estuary, Haiphong (Vietnam)     

Jean-Pierre Lefebvre  Sylvain Ouillon  Vu Duy Vinh  Robert Arfi  Jean-Yves Panché  Xavier Mari  Chu Van Thuoc  Jean-Pascal Torréton 《Geo-Marine Letters》2012,32(2):103-121

In the Bach Dang–Cam Estuary, northern Vietnam, mechanisms governing cohesive sediment aggregation were investigated in situ in 2008–2009. As part of the Red River delta, this estuary exhibits a marked contrast in hydrological conditions between the monsoon and dry seasons. The impact on flocculation processes was assessed by means of surveys of water discharge, suspended particulate matter concentration and floc size distributions (FSDs) conducted during a tidal cycle at three selected sites along the estuary. A method was developed for calculating the relative volume concentration for the modes of various size classes from FSDs provided by the LISST 100X (Sequoia Scientific Inc.). It was found that all FSDs comprised four modes identified as particles/flocculi, fine and coarse microflocs, and macroflocs. Under the influence of the instantaneous turbulent kinetic energy, their proportions varied but without significant modification of their median diameters. In particular, when the turbulence level corresponded to a Kolmogorov microscale of less than ∼235 μm, a major breakup of flocs resulted in the formation of particles/flocculi and fine microflocs. Fluctuations in turbulence level were governed by seasonal variations in freshwater discharge and by the tidal cycle. During the wet season, strong freshwater input induced a high turbulent energy level that tended to generate sediment transfer from the coarser size classes (macroflocs, coarse microflocs) to finer ones (particles/flocculi and fine microflocs), and to promote a transport of sediment seawards. During the dry season, the influence of tides predominated. The turbulent energy level was then only episodically sufficiently high to generate transfer of sediment between floc size classes. At low turbulent energy, modifications in the proportions of floc size classes were due to differential settling. Tidal pumping produced a net upstream transport of sediment. Associated with the settling of sediment trapped in a near-bed layer at low turbulent energy, this causes the silting up of the waterways leading to the harbour of Haiphong.  相似文献   

Flare-Shaped Acoustic Anomalies in the Water Column Along the Ecuadorian Margin: Relationship with Active Tectonics and Gas Hydrates     

Francois Michaud  Jean-Noël Proust  Alexandre Dano  Jean-Yves Collot  Grâce Daniella Guiyeligou  María José Hernández Salazar  Gueorgui Ratzov  Carlos Martillo  Hugo Pouderoux  Laure Schenini  Jean-Frederic Lebrun  Glenda Loayza 《Pure and Applied Geophysics》2016,173(10-11):3291-3303

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Thermal segmentation along the N. Ecuador–S. Colombia margin (1–4°N): Prominent influence of sedimentation rate in the trench     

Boris Marcaillou  George Spence  Kelin Wang  Jean-Yves Collot  Alessandra Ribodetti 《Earth and Planetary Science Letters》2008,272(1-2):296-308

Along the deformation front of the North Ecuador–South Colombia (NESC) margin, both surface heat flow and trench sediment thickness show prominent along-strike variations, indicating significant spatial variations in sedimentation rate. Investigating these variations helps us address the important question of how trench sedimentation influences the temperature distribution along the interplate contact and the extent of the megathrust seismogenic zone. We examine this issue by analysing 1/ a new dense reflection data set, 2/ pre-stack depth migration of selected multichannel seismic reflection lines, 3/ numerous newly-identified bottom-simulating reflectors and 4/ the first heat probe measurements in the region. We develop thermal models that include sediment deposition and compaction on the cooling oceanic plate as well as viscous corner flow in the mantle wedge. We estimate that the temperature from 60–150 °C to 350–450 °C, commonly associated with the updip and downdip limits of the seismogenic zone, extends along the plate interface over a downdip distance of 160 to 190 ± 20 km. We conclude that the updip limit of the seismogenic zone for the great megathrust earthquake of 1979 is associated with low-temperature (60–70 °C) processes. Our models also suggest that 60–70% of the two-fold decrease in measured heat flow from 3°N to 2.8°N is related to an abrupt southward increase in sedimentation rate in the trench. Such a change may potentially induce a landward shift of the 60–150 °C isotherms, and thus the updip limit of the seismogenic zone, by 10 to 20 km.  相似文献   

Eustatic and hydrodynamic controls on the architecture of a deep shelf sand bank (Celtic Sea)   总被引：3，自引：0，他引：3  

Jean-Yves Reynaud  Bernadette Tessier  Jean-Noël Proust  Robert Dalrymple  Tania Marsset  Marc De Batist  Jean-François Bourillet  & Gilles Lericolais 《Sedimentology》1999,46(4):703-721

The architecture of a tidal sand bank in the south-eastern Celtic Sea was examined using very high-resolution seismic surveys. The bank comprises four depositional units. The lowest unit 1 is characterized by gently dipping (1–8°) strata that strike parallel to the length of the bank. Unit 1 is erosionally overlain by unit 2, which forms the bulk of the bank. This unit consists of stacked sets of downcurrent-dipping (7–12°) master bedding formed by climbing, sinuous-crested tidal dunes that are up to 20 m high. These deposits are locally incised by an anastomosed channel network (unit 3) that may represent a buried swatchway system. The upper part of the bank comprises wave-related deposits that are mainly preserved on the bank flanks (unit 4). The outer bank surface is erosional. The bank is believed to have formed during the last post-glacial sea-level rise. The facies evolution from unit 1 to unit 3 indicates an upward increase in tidal energy, mainly characterized by the thickening of dune cross-bed sets in unit 2. The majority of bank growth is inferred to have occurred in water depths of the order of 60 m. This evolution was controlled by relative sea-level rise, which is likely to have caused an episode of tidal resonance with associated strong tidal currents that were responsible for the incision of the deep, cross-cutting channels of unit 3. The transition to wave-dominated sedimentation in unit 4 is related to the decay of resonance with continued sea-level rise.  相似文献   

Polyphase wrench tectonics in the southern french Massif Central: kinematic inferences from pre- and syntectonic granitoids     

Jean-Yves Roig  Michel Faure  Patrick Ledru 《International Journal of Earth Sciences》1996,85(1):138-153

In the Variscan French Massif Central, the South Limousin area consists of low- to medium-grade metamorphic rocks intruded by two granitic bodies. The structural and textural analyses of these plutons undertaken in parallel with the structural analysis of their host rocks allow us to characterize and to date different stages in the tectonic evolution of this area. This study shows that the South Limousin area experienced successivelly two strike-slip events along two geographically distinct shear zones, from north to south the left-lateral Estivaux and the right-lateral South Limousin strike-slip faults, respectively. These ductile faults subdivide the South Limousin into three structural units, from north to south they are the Upper Gneiss unit, Thiviers-Payzac unit .and Génis unit. The two granitic bodies intrude the Thiviers-Payzac unit only. The younger Estivaux granite is a syntectonic pluton which emplaced during left-lateral wrenching. ⁴⁰Ar/³⁹Ar dates from biotites indicate an Early Carboniferous age (346 ± 3 Ma). The older granite is a pretectonic body. It is the Ordovician Saut du Saumon augen orthogneiss in which detailed structural analyses show the polyphase nature of the solid-state deformation. Our microtectonic data indicate that the right-lateral motions overprint the left-lateral ones and produce apparently symmetrical fabrics.  相似文献   

The dammed Hikurangi Trough: a channel-fed trench blocked by subducting seamounts and their wake avalanches (New Zealand–France GeodyNZ Project)     

Keith B. Lewis  Jean-Yves Collot  & Serge E. Lallem 《Basin Research》1998,10(4):441-468

The Hikurangi Trough, off eastern New Zealand, is at the southern end of the Tonga–Kermadec–Hikurangi subduction system, which merges into a zone of intracontinental transform. The trough is mainly a turbidite-filled structural trench but includes an oblique-collision, foredeep basin. Its northern end has a sharp boundary with the deep, sediment-starved, Kermadec Trench. Swath-mapping, sampling and seismic surveys show modern sediment input is mainly via Kaikoura Canyon, which intercepts littoral drift at the southern, intracontinental apex of the trough, with minor input from seep gullies. Glacial age input was via many canyons and about an order of magnitude greater. Beyond a narrow, gravelly, intracontinental foredeep, the southern trench-basin is characterized by a channel meandering around the seaward edge of mainly Plio-Pleistocene, overbank deposits that reach 5 km in thickness. The aggrading channel has sandy turbidites, but low-backscatter, and long-wavelength bedforms indicating thick flows. Levées on both sides are capped by tangentially aligned mudwaves on the outsides of bends, indicating centrifugal overflow from heads of dense, fast-moving, autosuspension flows. The higher, left-bank levée also has levée-parallel mudwaves, indicating Coriolis and/or boundary currents effects on dilute flows or tail plumes. In the northern trough, basin-fill is generally less than 2 km thick and includes widespread overbank turbidites, a massive, blocky, avalanche deposit and an extensive, buried, debris flow deposit. A line of low seamounts on the subducting plate acts as a dam preventing modern turbidity currents from reaching the Kermadec Trench. Major margin collapse probably occurred in the wake of a large subducting seamount; this seamount and its wake debris flow probably dammed the trench from 2 Ma to 0.5 Ma. Before this, similar dams may have re-routed turbidity currents across the plateau.  相似文献   

Changes in structural and functional diversity of nematode communities during a spring phytoplankton bloom in the southern North Sea     

Jan Vanaverbeke  Maaike Steyaert  Karline Soetaert  Vronique Rousseau  Dirk Van Gansbeke  Jean-Yves Parent  Magda Vincx 《Journal of Sea Research》2004,52(4):588

The response of nematode communities to the sedimentation of a spring phytoplankton bloom in a sandy, well-oxygenated sediment at a single station (station 330) in the Southern North Sea was investigated monthly from early March to July 1999. Both structural (nematode density, diversity, vertical distribution and community composition) and functional (feeding type distributions, number of species within feeding groups) characteristics showed considerable changes shortly after the arrival of fresh organic material at the sediment surface. The general increase in numerical densities and diversity was related to changes within the groups of selective deposit-feeding and epistrate-feeding nematodes. It is hypothesised that sedimentation and subsequent remineralisation of fresh organic matter during the spring phytoplankton bloom result in an increase of suitable food items (both living and dead). This, combined with the availability of oxygen, creates conditions in which many nematode species can co-exist.  相似文献   

Seafloor mapping in the West,Southwest and South Pacific: Foreword     

Jean-Marie Auzende  Jean-Yves Collot 《Marine Geophysical Researches》1996,18(2-4):119-121

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